1. Field of the Invention
The present invention relates to coding and/or decoding of an audio signal, and more particularly, to a lossless audio coding/decoding method and apparatus capable of providing a greater compression ratio than in a bit-plane Golomb code (BPGC) using a text-based coding method.
2. Description of the Related Art
Lossless audio coding methods include Meridian lossless audio compression coding, Monkey's audio coding, and free lossless audio coding. Meridian lossless packing (MLP) is applied and used in a digital versatile disk-audio (DVD-A). As the bandwidth of Internet network increases, a large volume of multimedia contents can be provided. In the case of audio contents, a lossless audio method is needed. In the European Union (EU), digital audio broadcasting has already begun through digital audio broadcasting (DAB), and broadcasting stations and contents providers for this are using lossless audio coding methods. In response to this, MPEG group is also proceeding with standardization for lossless audio compression under the name of ISO/IEC 14496-3:2001/AMD 5, Audio Scalable to Lossless Coding (SLS). This provides fine grain scalability (FGS) and enables lossless audio compression.
A compression ratio, which is the most important factor in a lossless audio compression technology, can be improved by removing redundant information between data items. The redundant information can be removed by prediction between neighboring data items and can also be removed by a context between neighboring data items.
Integer modified discrete cosine transform (MDCT) coefficients show a Laplacian distribution, and in this distribution, a compression method named Golomb code shows an optimal result. In order to provide the FGS, bit-plane coding is needed and a combination of the Golomb code and bit-plane coding is referred to as bit plane Golomb coding (BPGC), which provides an optimal compression ratio and FGS. However, in some cases the assumption that the integer MDCT coefficients show a Laplacian distribution is not correct in an actual data distribution. Since the BPGC is an algorithm devised assuming that integer MDCT coefficients show a Laplacian distribution, if the integer MDCT coefficients do not show a Laplacian distribution, the BPGC cannot provide an optimal compression ratio. Accordingly, a lossless audio coding and decoding method capable of providing an optimal compression ratio regardless of the assumption that the integer MDCT coefficients show a Laplacian distribution is needed.